The present invention relates to loudspeaker systems. More particularly, the invention relates to an improved coaxial loudspeaker system.
Loudspeaker systems typically include two or more separate speakers (sometimes referred to as “drivers”), each configured for reproducing sounds within a selected audio frequency band. For example, a loudspeaker system may include a woofer speaker for reproducing sounds in a relatively low frequency band, a mid-range speaker for reproducing sounds in a mid-range frequency band, and a tweeter speaker for reproducing sounds in a relatively high frequency band. Those skilled in the art will appreciate that any number of speakers including sub-woofers, super tweeters, etc. may also be provided. Multi-speaker loudspeaker systems also include a crossover filter network or circuit for separating an incoming electrical audio signal into separate bands for delivery to the voice coils of the separate speakers to ensure that each speaker only receives audio signals corresponding to its frequency band.
It is common to mount the individual speakers of a loudspeaker system in an enclosure in a vertically or horizontally spaced-apart orientation. Unfortunately, this results in mis-alignment of the acoustic centers of the speakers. Because listeners are typically not the same distance and/or angle from all of the individual speakers, sounds from some of the speakers reach the listeners before the sounds from other speakers, causing an uneven or nonuniform overall sound reproduction, especially for frequencies near the crossover regions of the speakers.
Coaxial speaker systems have been developed to greatly minimize the above-described problems associated with conventional speaker systems. Coaxial speakers include two or more separate speakers that are mounted on a common central axis, typically with a high frequency speaker mounted inside of a low frequency speaker. In coaxial speaker systems, there is no vertical or horizontal offset of the acoustic centers of the speakers and therefore greatly reduced offset of sounds emanating from the speakers. The only remaining offset may be in the separation of the acoustic centers of the drivers along the common central axis.
Applicant has discovered, however, that coaxial speakers may suffer from their own limitations. Specifically, applicant has discovered that some of the sound waves from the high frequency speaker may be projected rearward toward the low frequency speaker, due to a combination of edge diffraction and insufficient directivity control, and bounce or reflect off the low frequency speaker. These reflected sound waves cause undesirable variations in the performance and undesirable off-axis lobes in the spatial performance of the speaker system due to the path length differences between the direct sound from the high frequency speaker and the reflections of these sounds from the low frequency speaker.
Accordingly, there is a need for an improved coaxial speaker that overcomes the limitations of known existing coaxial speakers.